I may be repeating myself, but I just don’t understand the gain. It often seems like this at my work too, with the justification "IT IS SO".
The gain becomes especially clear in more traditional constellations with children. This usually plays out in such a way that the woman accepts a loss of income to take over early childhood education, while the man is not prevented from his full-time job (Yes, I know other models are becoming popular. That’s a good thing as well). Here it becomes clear that one can do what they do only because the other creates a balance. However, not all of this work is reflected in a monetary equivalent; caregiving work doesn’t even generate pension entitlements. It therefore seems logical that in the event of a divorce, compensation is sought afterward.
In your specific constellation without children, the gain is certainly smaller. But just saying "hey, she’s only doing what she wants" is still not enough: if she didn’t do it, you would have to do it or alternatively pay for the corresponding service (or simply go without it). So a value is created within the relationship, but it is not visible in the form of capital, rather in the form of time.
Since you would pay off and maintain your house even without that, and you “compensate” the gained time through rent-free living, I can understand your approach. Maybe the "common-law marriage" is simply the better lifestyle for you?